It's the first time since democracy was restored in Spain in 1975 that a direct member of King Juan Carlos' family has faced preliminary charges of any kind, in any case, a spokesman for the Royal Household said.

Urdangarin, the king's son-in-law, already faces preliminary charges as a suspect in the fraud scandal that has created unprecedented problems for the popular royal family. He denies any wrongdoing.

Now, both the princess and her husband are under investigation for allegedly diverting public funds earmarked for a non-profit foundation for private use.

Late Wednesday, the Royal Household issued a statement saying it was surprised that the judge -- who last year said in an order that there were insufficient grounds to name the princess as a suspect with preliminary charges in the case -- had changed his mind.

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In his 18-page order Wednesday, the judge said that further investigation since last year had led to the decision to bring preliminary charges.

The Royal Household statement also said that it is in "absolute conformity" with an announcement by prosecutors that they will appeal the judge's order to place preliminary charges on the princess.

The Royal Household statement added that it maintains full respect for judicial decisions.

Earlier Wednesday, the Royal Household press office tersely said that it does not comment on judicial decisions. But the story about the King's daughter dominated the news in Spain and was getting prominent coverage abroad as well.

Finally, the Royal Household opted for its statement late in the day, after the prosecutors announced their move, a senior spokesman told CNN.

The judge's order said Princess Cristina will be questioned on April 27 regarding "the handling and destination of funds obtained" through her husband's foundation and also a separate company.

Urdangarin was granted the title of Duke of Palma when he married Princess Cristina, the king's youngest daughter, in 1997.

Judge Castro is leading the investigation at a local court in Palma de Mallorca, in Spain's Balearic Islands.

An adviser to the royal household also has been implicated in the scandal.

Earlier this year, a judge ordered Urdangarin and a former business associate, Diego Torrres, to deposit a joint bond of 8 million euros ($10.8 million) for potential civil damages. If not, the judge would move to embargo the assets of the two men, a court spokeswoman said.

No trial has been set in the case, which has riveted national attention. Although preliminary charges have been announced, they could eventually be dropped, but a filing of indictments would set a trial in motion.